Added docs about logback-spring and props
Added docs about logback-spring and props

we had a couple of questions related to missing attributes in the logback file or the logs as such. It's related to the fact that once you provide a custom logback file you have to place the propery of spring.application.name in the bootstrap file

fixes #376

spring-cloud/spring-cloud-sleuth,marcingrzejszczak/spring-cloud-sleuth,marcingrzejszczak/spring-cloud-sleuth,marcingrzejszczak/spring-cloud-sleuth,spring-cloud/spring-cloud-sleuth,marcingrzejszczak/spring-cloud-sleuth,spring-cloud/spring-cloud-sleuth,spring-cloud/spring-cloud-sleuth,spring-cloud/spring-cloud-sleuth